package test;
import java.util.*;

interface IntegerStack{
	public Integer push(Integer item);
	public Integer pop();
	public Integer peek();
	public boolean empty();
	public int size();
}

class ArrayListIntegerStack implements IntegerStack{


	private List<Integer> list;

	public  ArrayListIntegerStack() {
		list = new ArrayList<Integer>();
	}
	
	@Override
	public Integer push(Integer item) {
		if(item ==null)
			return null;
		list.add(item);
		return item;
	}

	@Override
	public Integer pop() {
		if(list.isEmpty())
		return null;
		return list.remove(list.size()-1);
		
	}

	@Override
	public Integer peek() {
		if(list.isEmpty())
			return null;
		return list.get(list.size()-1);
	}

	@Override
	public boolean empty() {
		if(list.isEmpty())
		return true;
		return false;
	}

	@Override
	public int size() {
		
		return list.size();
	}
	
	@Override
	public String toString() {
		return list.toString() ;
	}
}
public class Main {
	public static void main(String[] args) {
		Scanner in = new Scanner(System.in);
		int m = in.nextInt();
		ArrayListIntegerStack list = new ArrayListIntegerStack();
		for (int i = 0; i < m; i++) {
			System.out.println(list.push(in.nextInt()));
		}
		System.out.println(list.peek()+","+list.empty()+","+list.size());
		System.out.println(list.toString());
		int x = in.nextInt();
		for (int i = 0; i < x; i++) {
			System.out.println(list.pop());
			
		}
		System.out.println(list.peek()+","+list.empty()+","+list.size());
		System.out.println(list.toString());
	}
}
